Several lines of pharmacological and genetic evidence support the role of Melanin Concentrating Hormone Receptor-1 (hereafter “MCHR1”) as a modulator of food intake and body weight. Central administration of MCH increases food intake and body weight in both rats and mice. Chronic ICV infusion of MCH causes increased food intake and ultimately obesity in mice, while infusion of an MCH peptide antagonist blocks MCH-induced food intake and results in weight loss and decreased feeding in diet-induced obese mice.
The expression of both the MCH peptide and receptor are modulated by nutritional status. MCH mRNA is upregulated both in hyperphagic obese mice (ob/ob), and fasted animals. Targeted disruption of the gene for MCH peptide results in hypophagia and leanness. Disruption of the MCHR1 gene causes leanness, altered metabolism, and hyperlocomotion accompanied by mild hyperphagia. Conversely, over-expression of MCH peptide results in hyperphagia, obesity and diabetes. Small molecule MCHR1 antagonists have been shown to cause weight loss in rodent weight and feeding models after both oral and intraperitoneal administration; Eur. J. Pharmacol., 438:129-135 (2002), Nat. Med., 8:825-830 (2002), Eur. J. Pharmacol., 497:41-47 (2004).
MCHR1 has also been reported to play a key role in the pathogenesis of acute experimental colitis and possibly human IBD (inflammatory bowel disease). It has been shown that immunoneutralization is an effective treatment for TNBS-induced colitis. Kokkotou, E. et al., “Melanin-concentrating hormone as a mediator of intestinal inflammation”, Proc. Natl. Acad. Sci., 105(30):10613-10618 (Jul. 29, 2008).
In addition, MCH and MCHR1 has also been reported to play a role in the endocrine and behavioral responses to stress. Treatment of rats and mice with MCHR antagonists produce a robust anti-depressant and anti-anxiolytic effect. (JPET DOI:10.1124/jpet.108.143362).
Numerous non-peptide MCHR1 antagonists have been disclosed. The scope of the genus for each reflects a common perception regarding the criteria required for ligand recognition as MCHR1 agonists. A recent review of MCHR1 patent disclosures emphasized the commonality of these structures by the following description; “Ubiquitous throughout the MCH patent literature are molecules consisting of a central scaffold to which linkers to an aryl or heteroaryl group and a basic amino functionality are attached” (Kowalski, Ti. et al., Exp. Opin. Invest. Drugs, 13:1113-1122 (2004)). Pharmacophore models of these geni consistently envision a presumed prerequisite electrostatic interaction between a basic amine center of the antagonist ligand and aspartic acid 123 of the receptor which presumably is envisaged to emulate the mandatory interaction between arginine 14 of MCH peptide agonists with aspartic acid 123 of the MCHR1 receptor. (Ulven, T. et al., J. Med. Chem., 48:5684-5697 (2005)). However, incorporation of this basic amine in a MCHR1 antagonist increases substantially the probability of binding to off-target ion-channels and biogenic amine receptors.
U.S. Publication No. 2007/0093509 A1 published Apr. 26, 2007 discloses a series of novel high affinity selective MCHR1 antagonists of formula A:
wherein,
A is phenyl or a monocyclic heteroaryl;
D is CH2 or a direct bond;
R1 is independently selected from hydrogen, halogen, lower alkyl, lower cycloalkyl, CF3, OR6 or SR6;
R2 is hydrogen or lower alkyl;
R4 is hydroxyl or G-D2-Zn;
n is an integer from 1 to 3;
R5 is hydrogen, halogen, lower alkyl, lower cycloalkyl, CF3, SR6, lower alkoxy, lower cycloalkoxy, CN, CONR7R7, SOR6, SO2R6, NR7COR7, NR7CO2R7, CO2R6, heteroaryl, NR7SO2R6 or COR6;
G is O, S or CR7R7,
D2 is a direct bond, lower alkyl, lower cycloalkyl or a 4 to 6-membered non-basic heterocycle;
Z is hydrogen, hydroxyl, lower alkoxy, lower cycloalkoxy, OCONR7R7, CN, CONR7R7, SOR6, SO2R6, NR7COR7, NR7CO2R7, CO2R6, heteroaryl, NR6SO2R6 or COR6;
R6 is independently selected from lower alkyl or lower cycloalkyl; and
R7 is independently selected from hydrogen, lower alkyl or lower cycloalkyl, wherein two R7 and the atom to which they are attached may optionally form a ring of 4 to 7 atoms.
There is currently a need in the art for additional small molecule antagonists of MCHR1.